1. According to Arrhenius, an acid is a substance that:
A) Accepts a proton
B) Donates a proton
C) Increases H⁺ ions in aqueous solution
D) Increases OH⁻ ions in aqueous solution
Answer: C
Explanation: Arrhenius acid increases concentration of H⁺ (or H₃O⁺) ions in water.
2. According to Arrhenius, a base is a substance that:
A) Accepts a proton
B) Increases OH⁻ ions in aqueous solution
C) Donates H⁺ ions
D) Produces CO₃²⁻ ions
Answer: B
Explanation: Arrhenius base increases OH⁻ ions in aqueous solution.
3. According to Brønsted-Lowry, acids:
A) Donate protons
B) Accept protons
C) Donate electrons
D) Accept electrons
Answer: A
Explanation: Brønsted-Lowry acid is proton donor.
4. According to Brønsted-Lowry, bases:
A) Donate protons
B) Accept protons
C) Donate electrons
D) Accept electrons
Answer: B
Explanation: Brønsted-Lowry base is proton acceptor.
5. Lewis acid is:
A) Proton donor
B) Electron pair donor
C) Electron pair acceptor
D) Proton acceptor
Answer: C
Explanation: Lewis acid accepts an electron pair.
6. Lewis base is:
A) Electron pair donor
B) Electron pair acceptor
C) Proton donor
D) Proton acceptor
Answer: A
Explanation: Lewis base donates an electron pair.
7. Strong acids:
A) Partially ionize in water
B) Completely ionize in water
C) Are weak electrolytes
D) Do not conduct electricity
Answer: B
Explanation: Strong acids completely dissociate in water → strong electrolytes.
8. Weak acids:
A) Partially ionize in water
B) Completely ionize
C) Are strong electrolytes
D) React with water only
Answer: A
Explanation: Weak acids partially dissociate → weak electrolytes.
9. Which of the following is a strong acid?
A) HCl
B) CH₃COOH
C) H₂CO₃
D) HF
Answer: A
Explanation: HCl completely ionizes in water → strong acid.
10. Which of the following is a weak acid?
A) HNO₃
B) H₂SO₄
C) CH₃COOH
D) HCl
Answer: C
Explanation: Acetic acid is partially ionized → weak acid.
11. Strong bases:
A) Partially ionize
B) Completely ionize
C) Weak electrolytes
D) Neutral
Answer: B
Explanation: Strong bases like NaOH, KOH completely ionize in water.
12. Weak bases:
A) Partially ionize
B) Completely ionize
C) Strong electrolytes
D) Neutral
Answer: A
Explanation: Weak bases like NH₃ partially accept protons in water.
13. Amphoteric substances:
A) Act as acids only
B) Act as bases only
C) Act as both acids and bases
D) Neutral
Answer: C
Explanation: Example: H₂O, Al(OH)₃, ZnO can act as acid or base.
14. Example of amphoteric oxide:
A) Na₂O
B) ZnO
C) CO₂
D) SO₃
Answer: B
Explanation: ZnO reacts with acids and bases → amphoteric.
15. Example of amphoteric hydroxide:
A) NaOH
B) Al(OH)₃
C) KOH
D) Ca(OH)₂
Answer: B
Explanation: Al(OH)₃ reacts with HCl (acid) and NaOH (base).
16. pH of neutral solution at 25°C is:
A) 0
B) 7
C) 14
D) 1
Answer: B
Explanation: Neutral solution [H⁺] = [OH⁻] → pH = 7.
17. pH of strong acid (0.01 M HCl) is:
A) 2
B) 12
C) 7
D) 1
Answer: A
Explanation: pH = -log[H⁺] = -log(0.01) = 2.
18. pOH of neutral solution:
A) 7
B) 0
C) 14
D) 1
Answer: A
Explanation: pH + pOH = 14 → for neutral, pOH = 7.
19. Salt formed from strong acid and strong base is:
A) Neutral
B) Acidic
C) Basic
D) Amphoteric
Answer: A
Explanation: Example: NaCl (HCl + NaOH) → neutral.
20. Salt formed from strong acid and weak base is:
A) Neutral
B) Acidic
C) Basic
D) Amphoteric
Answer: B
Explanation: Example: NH₄Cl → acidic solution.
21. Salt formed from weak acid and strong base is:
A) Neutral
B) Acidic
C) Basic
D) Amphoteric
Answer: C
Explanation: Example: Na₂CO₃ → basic solution.
22. Salt formed from weak acid and weak base is:
A) Neutral
B) Acidic or basic depending on Kₐ and K_b
C) Strongly acidic
D) Strongly basic
Answer: B
Explanation: pH depends on relative strengths of acid and base.
23. Hydrolysis of Na₂CO₃ makes solution:
A) Neutral
B) Acidic
C) Basic
D) Amphoteric
Answer: C
Explanation: CO₃²⁻ reacts with water → OH⁻ → basic solution.
24. Hydrolysis of NH₄Cl makes solution:
A) Neutral
B) Acidic
C) Basic
D) Amphoteric
Answer: B
Explanation: NH₄⁺ reacts with water → H⁺ → acidic solution.
25. Universal indicator shows strong acid as:
A) Red
B) Blue
C) Green
D) Violet
Answer: A
Explanation: Red color indicates strong acid (pH 0–3).
26. Strong acids have:
A) Small Ka
B) Large Ka
C) Small Kb
D) No dissociation
Answer: B
Explanation: Strong acids completely ionize → large acid dissociation constant (Ka).
27. Weak acids have:
A) Small Ka
B) Large Ka
C) Small Kb
D) Large Kb
Answer: A
Explanation: Weak acids partially ionize → small Ka.
28. Strong bases have:
A) Small Kb
B) Large Kb
C) Small Ka
D) Large Ka
Answer: B
Explanation: Strong bases completely ionize → large base dissociation constant (Kb).
29. Weak bases have:
A) Small Kb
B) Large Kb
C) Small Ka
D) Large Ka
Answer: A
Explanation: Weak bases partially ionize → small Kb.
30. Indicator for strong acid vs strong base titration:
A) Methyl orange
B) Phenolphthalein
C) Both A & B
D) Litmus
Answer: C
Explanation: Both can be used; phenolphthalein preferred for sharp endpoint.
31. Indicator for strong acid vs weak base titration:
A) Methyl orange
B) Phenolphthalein
C) Litmus
D) Bromothymol blue
Answer: A
Explanation: Methyl orange changes color at acidic endpoint (pH ≈ 3.1–4.4).
32. Indicator for weak acid vs strong base titration:
A) Methyl orange
B) Phenolphthalein
C) Bromothymol blue
D) Litmus
Answer: B
Explanation: Endpoint is basic → phenolphthalein changes color at pH 8.2–10.0.
33. Buffer solution resists change in:
A) pH on adding acid
B) pH on adding base
C) Both A & B
D) Neither
Answer: C
Explanation: Buffers contain weak acid + conjugate base or weak base + conjugate acid → resist pH changes.
34. Example of acidic buffer:
A) CH₃COOH + CH₃COONa
B) NH₄OH + NH₄Cl
C) NaOH + NaCl
D) HCl + NaCl
Answer: A
Explanation: Weak acid + its salt → acidic buffer solution.
35. Example of basic buffer:
A) NH₄OH + NH₄Cl
B) CH₃COOH + CH₃COONa
C) NaOH + NaCl
D) HCl + NaCl
Answer: A
Explanation: Weak base + its salt → basic buffer solution.
36. pH of acidic buffer is:
A) < 7
B) 7
C) > 7
D) 14
Answer: A
Explanation: Acidic buffer has pH < 7 due to weak acid presence.
37. pH of basic buffer is:
A) < 7
B) 7
C) > 7
D) 0
Answer: C
Explanation: Basic buffer has pH > 7 due to weak base presence.
38. pH of a buffer depends on:
A) Ratio of conjugate base to acid
B) Concentration of salt only
C) Temperature only
D) Indicator used
Answer: A
Explanation: Henderson-Hasselbalch equation: pH = pKa + log([A⁻]/[HA]).
39. Neutralization reaction is:
A) Acid + acid → salt + water
B) Base + base → salt + water
C) Acid + base → salt + water
D) Salt + water → acid + base
Answer: C
Explanation: Neutralization: H⁺ from acid + OH⁻ from base → H₂O + salt.
40. Product of HCl + NaOH reaction:
A) NaCl + H₂O
B) NaOH + H₂O
C) NaCl only
D) H₂O only
Answer: A
Explanation: Strong acid + strong base → neutral salt (NaCl) + water.
41. Product of CH₃COOH + NaOH reaction:
A) CH₃COONa + H₂O
B) NaOH + H₂O
C) CH₃COOH + NaOH
D) H₂O only
Answer: A
Explanation: Weak acid + strong base → basic salt (CH₃COONa) + water.
42. Salt from strong acid + weak base is:
A) Acidic
B) Neutral
C) Basic
D) Amphoteric
Answer: A
Explanation: Example: NH₄Cl → acidic solution.
43. Salt from weak acid + strong base is:
A) Acidic
B) Neutral
C) Basic
D) Amphoteric
Answer: C
Explanation: Example: Na₂CO₃ → basic solution.
44. Hydrolysis of salts is:
A) Reaction with water to form acid/base
B) Reaction with acid only
C) Reaction with base only
D) None
Answer: A
Explanation: Salt ions react with water → solution becomes acidic/basic/neutral.
45. Indicator changes color at:
A) Specific pH range
B) Any pH
C) Only neutral pH
D) Only strong acids
Answer: A
Explanation: Indicators are weak acids/bases → color depends on pH.
46. Methyl orange changes from red to yellow over pH:
A) 3.1–4.4
B) 8.2–10.0
C) 6.0–7.6
D) 0–2
Answer: A
Explanation: Red in acid, yellow in base → transition pH 3.1–4.4.
47. Phenolphthalein changes from colorless to pink over pH:
A) 3.1–4.4
B) 8.2–10.0
C) 6.0–7.6
D) 0–2
Answer: B
Explanation: Colorless in acid, pink in basic solution → transition pH 8.2–10.0.
48. Universal indicator shows basic solution as:
A) Blue to violet
B) Red to orange
C) Green
D) Yellow
Answer: A
Explanation: pH > 7 – blue/violet color.
49. Acid-base titration is used to determine:
A) Strength of acid/base
B) Concentration of acid/base
C) Both A & B
D) None
Answer: B
Explanation: Titration measures unknown concentration using standard solution.
50. Salt from weak acid + weak base:
A) pH depends on relative strengths
B) Always neutral
C) Always acidic
D) Always basic
Answer: A
Explanation: Example: NH₄CH₃COO → pH depends on Kb of NH₄⁺ and Ka of CH₃COOH.
51. Hydrolysis of a salt refers to:
A) Reaction with acid to form salt
B) Reaction with base to form salt
C) Reaction with water producing acidic, basic, or neutral solution
D) Decomposition on heating
Answer: C
Explanation: Salt ions react with water → may give acidic, basic, or neutral solution.
52. Salt of strong acid and strong base:
A) Undergoes hydrolysis → acidic
B) Undergoes hydrolysis → basic
C) Does not hydrolyze → neutral solution
D) Amphoteric
Answer: C
Explanation: Example: NaCl → neutral solution, no hydrolysis.
53. Salt of strong acid and weak base:
A) Acidic solution
B) Basic solution
C) Neutral
D) Amphoteric
Answer: A
Explanation: Example: NH₄Cl → NH₄⁺ hydrolyzes → H⁺ → acidic.
54. Salt of weak acid and strong base:
A) Acidic solution
B) Basic solution
C) Neutral
D) Amphoteric
Answer: B
Explanation: Example: Na₂CO₃ → CO₃²⁻ hydrolyzes → OH⁻ → basic.
55. Salt of weak acid and weak base:
A) Neutral
B) Acidic or basic depending on Ka and Kb
C) Always acidic
D) Always basic
Answer: B
Explanation: Example: NH₄CH₃COO → pH depends on Kb(NH₄⁺) and Ka(CH₃COOH).
56. Common ion effect:
A) Suppression of ionization by presence of common ion
B) Enhancement of ionization
C) No effect
D) Only for acids
Answer: A
Explanation: Presence of common ion shifts equilibrium → reduces ionization.
57. Common ion effect decreases:
A) Solubility of salts
B) Ionization of acids/bases
C) Both A & B
D) None
Answer: C
Explanation: Both solubility and ionization suppressed in presence of common ions.
58. Solubility product (Ksp) represents:
A) Concentration of solute in solution
B) Product of ionic concentrations at saturation
C) pH of solution
D) None
Answer: B
Explanation: Ksp = [Mⁿ⁺]^m × [X^m⁻]^n for salt MmXn at saturation.
59. Precipitation occurs when:
A) Ionic product > Ksp
B) Ionic product < Ksp
C) Ionic product = Ksp
D) Solution is neutral
Answer: A
Explanation: When ionic product exceeds solubility product → excess ions form precipitate.
60. Example of precipitation reaction:
A) AgNO₃ + NaCl → AgCl + NaNO₃
B) HCl + NaOH → NaCl + H₂O
C) Na₂CO₃ + HCl → NaCl + CO₂ + H₂O
D) BaCl₂ + H₂O → Ba²⁺ + 2Cl⁻
Answer: A
Explanation: AgCl precipitates → insoluble in water.
61. Salt formed from strong acid and strong base:
A) NaCl
B) NH₄Cl
C) Na₂CO₃
D) NH₄CH₃COO
Answer: A
Explanation: HCl + NaOH → NaCl (neutral).
62. Salt formed from strong acid and weak base:
A) NH₄Cl
B) NaCl
C) Na₂CO₃
D) K₂SO₄
Answer: A
Explanation: NH₄⁺ hydrolyzes → acidic solution.
63. Salt formed from weak acid and strong base:
A) Na₂CO₃
B) NaCl
C) NH₄Cl
D) KCl
Answer: A
Explanation: CO₃²⁻ hydrolyzes → basic solution.
64. Salt formed from weak acid and weak base:
A) NH₄CH₃COO
B) NaCl
C) KCl
D) Na₂SO₄
Answer: A
Explanation: pH depends on relative strengths of acid & base.
65. Solubility of CaSO₄ in water is low because:
A) Ksp is small
B) Ksp is large
C) Ionic product is high
D) pH is neutral
Answer: A
Explanation: Low Ksp → low solubility.
66. Solubility of AgCl decreases in NaCl solution due to:
A) Common ion effect
B) Increased temperature
C) Hydrolysis
D) Neutralization
Answer: A
Explanation: Cl⁻ ions from NaCl reduce AgCl solubility.
67. NaHCO₃ reacts with HCl to form:
A) NaCl + CO₂ + H₂O
B) NaOH + CO₂
C) NaCl + H₂O
D) Na₂CO₃ + H₂O
Answer: A
Explanation: Acid reacts with bicarbonate → salt + CO₂ + water.
68. Na₂CO₃ reacts with HCl to form:
A) NaCl + CO₂ + H₂O
B) NaOH + CO₂
C) NaCl only
D) NaHCO₃
Answer: A
Explanation: Carbonate reacts with acid → produces CO₂, water, and salt.
69. Na₂CO₃ reacts with Ca(OH)₂ to form:
A) CaCO₃ + 2NaOH
B) NaOH + H₂O
C) Na₂CaO₂
D) CaCl₂
Answer: A
Explanation: Double displacement → precipitate CaCO₃ + NaOH in solution.
70. Reaction of NaOH with NH₄Cl produces:
A) NH₃ + H₂O + NaCl
B) NH₄OH only
C) NaNH₂
D) NH₄NO₃
Answer: A
Explanation: Strong base liberates NH₃ from ammonium salt.
71. Reaction of Na₂CO₃ with H₂O produces:
A) Basic solution (Na⁺ + CO₃²⁻ + H₂O → OH⁻)
B) Acidic solution
C) Neutral solution
D) None
Answer: A
Explanation: CO₃²⁻ hydrolyzes → OH⁻ → basic solution.
72. Applications of salts:
A) Fertilizers
B) Medicines
C) Food preservatives
D) All of these
Answer: D
Explanation: Salts have diverse applications in industry, medicine, and food.
73. Baking soda (NaHCO₃) is used:
A) As antacid
B) In baking
C) Both
D) None
Answer: C
Explanation: Neutralizes acid (antacid) and releases CO₂ in baking.
74. Washing soda (Na₂CO₃·10H₂O) is used:
A) In soap and detergent
B) In baking
C) As antacid
D) Fertilizer
Answer: A
Explanation: Reacts with Ca²⁺/Mg²⁺ ions in water → softens water.
75. Common salt (NaCl) is used:
A) Food seasoning
B) Chemical industry
C) Both
D) None
Answer: C
Explanation: NaCl is essential for food and industrial chemical processes.
76. Bromothymol blue changes color in pH range:
A) 6.0–7.6
B) 3.1–4.4
C) 8.2–10.0
D) 0–2
Answer: A
Explanation: Yellow in acid, green at neutral, blue in basic solution.
77. Neutralization point in strong acid–strong base titration occurs at:
A) pH < 7
B) pH = 7
C) pH > 7
D) pH = 14
Answer: B
Explanation: Strong acid + strong base → neutral solution at equivalence.
78. Neutralization point in strong acid–weak base titration occurs at:
A) pH < 7
B) pH = 7
C) pH > 7
D) pH = 14
Answer: A
Explanation: Salt formed (e.g., NH₄Cl) is acidic → pH < 7.
79. Neutralization point in weak acid–strong base titration occurs at:
A) pH < 7
B) pH = 7
C) pH > 7
D) pH = 0
Answer: C
Explanation: Salt formed (e.g., Na₂CO₃) is basic → pH > 7.
80. Indicator choice depends on:
A) Type of acid & base
B) Equivalence point pH
C) Both A & B
D) Color of solution
Answer: C
Explanation: Indicator must change color at pH near equivalence point.
81. Phenolphthalein is colorless in:
A) Acidic solution
B) Neutral solution
C) Basic solution
D) All
Answer: A
Explanation: Phenolphthalein turns pink in basic solution; colorless in acid.
82. Methyl orange is red in:
A) Acid
B) Base
C) Neutral
D) Both A & B
Answer: A
Explanation: Red in acidic medium, yellow in basic medium.
83. Universal indicator shows pH 7 as:
A) Red
B) Green
C) Blue
D) Violet
Answer: B
Explanation: Green indicates neutral pH.
84. Acid rain is caused by:
A) SO₂ and NO₂ dissolution in rainwater
B) CO₂ dissolution only
C) O₂ only
D) N₂ only
Answer: A
Explanation: SO₂ and NO₂ form H₂SO₄ and HNO₃ → acid rain.
85. Effect of acid rain on soil:
A) Reduces fertility
B) Increases pH
C) No effect
D) Makes soil basic
Answer: A
Explanation: Acid rain leaches nutrients → soil fertility decreases.
86. Buffer solution in blood:
A) H₂CO₃ / HCO₃⁻
B) NH₄⁺ / NH₃
C) CH₃COOH / CH₃COONa
D) NaCl / HCl
Answer: A
Explanation: Carbonic acid-bicarbonate buffer maintains blood pH ≈ 7.4.
87. Blood pH lower than 7.35 causes:
A) Alkalosis
B) Acidosis
C) Neutral
D) None
Answer: B
Explanation: Acidic blood → acidosis.
88. Blood pH higher than 7.45 causes:
A) Acidosis
B) Alkalosis
C) Neutral
D) None
Answer: B
Explanation: Alkalosis occurs → blood too basic.
89. OH⁻ concentration of neutral solution at 25°C:
A) 1 × 10⁻⁷ M
B) 1 × 10⁻¹⁴ M
C) 1 × 10⁻⁴ M
D) 1 × 10⁻¹ M
Answer: A
Explanation: For neutral solution, [H⁺] = [OH⁻] = 10⁻⁷ M.
90. H⁺ concentration of neutral solution at 25°C:
A) 1 × 10⁻⁷ M
B) 1 × 10⁻¹⁴ M
C) 1 × 10⁻⁴ M
D) 1 × 10⁻¹ M
Answer: A
Explanation: Neutral solution: [H⁺] = 10⁻⁷ M.
91. Indicators are:
A) Weak acids or weak bases
B) Strong acids
C) Strong bases
D) Salts
Answer: A
Explanation: They change color depending on pH.
92. Acid-base theories used in chemistry:
A) Arrhenius
B) Brønsted-Lowry
C) Lewis
D) All of these
Answer: D
Explanation: All three theories describe acids and bases differently.
93. Industrial application of acid:
A) H₂SO₄ in fertilizer production
B) HCl in metal cleaning
C) Both A & B
D) None
Answer: C
Explanation: Strong acids are widely used in industry.
94. Industrial application of base:
A) NaOH in soap manufacturing
B) Ca(OH)₂ in water treatment
C) Both A & B
D) None
Answer: C
Explanation: Bases are used for cleaning, soap making, water softening.
95. Lime (CaO) is used in:
A) Water treatment
B) Cement production
C) Both
D) None
Answer: C
Explanation: Lime neutralizes acidic water and is used in cement.
96. Na₂CO₃ is used in:
A) Glass making
B) Water softening
C) Soap production
D) All of these
Answer: D
Explanation: Sodium carbonate has multiple industrial uses.
97. Alkalinity of water is due to:
A) Carbonates and bicarbonates
B) Chlorides
C) Sulfates
D) Nitrates
Answer: A
Explanation: CO₃²⁻ and HCO₃⁻ neutralize acids → alkaline water.
98. Acidity of water is due to:
A) Dissolved CO₂ → H₂CO₃
B) NaOH
C) CaCO₃
D) KCl
Answer: A
Explanation: CO₂ forms carbonic acid → makes water slightly acidic.
99. Common indicator for titrating strong acid vs weak base:
A) Methyl orange
B) Phenolphthalein
C) Litmus
D) Bromothymol blue
Answer: A
Explanation: Endpoint acidic → methyl orange changes color at low pH.
100. Common indicator for titrating weak acid vs strong base:
A) Methyl orange
B) Phenolphthalein
C) Bromothymol blue
D) Litmus
Answer: B
Explanation: Endpoint basic → phenolphthalein changes color in basic pH.